Gas sensor

Abstract

A gas sensor has a sensor element, extending axially, that detects a particular gas component in a gas under measurement, a metal housing causing the end of the sensor element to protrude farther than the end thereof to expose it to the gas under measurement and that surrounds the periphery of the sensor element and an outer tube disposed at the rear end inside the metal housing and a seal member that is disposed farther to the rear than the detection element and also inside the rear end of the outer tube, and that has formed therein a atmosphere-introduction hole passing therethrough in the axial direction, the gas sensor further having a crimped part, formed in the outer tube, for the purpose of holding the seal member a hollow-cylindrical member in contact with the inner peripheral surface of the atmosphere-introduction hole so as to oppose the crimped part, and a metal filter that joins to the hollow-cylindrical member at the rear end of the hollow-cylindrical member and also farther to the rear than the crimped part.

1. A gas sensor comprising:
 a detection element, extending in the axial direction, that detects a particular gas component in a gas under measurement; 
 a casing surrounding a periphery of the detection element and having a front end from which a front end of the detection element protrudes so that the front end of the detection element is exposed to the gas under measurement; 
 a seal member disposed on a rear side with respect to the detection element and also inside the rear end of the casing, the seal member having a ventilation hole penetrating therethrough in the axial direction; 
 a crimped part of the casing holding the seal member; 
 a hollow-cylindrical member being in contact with an inner peripheral surface of the ventilation hole and being located opposed to and being held in place by the crimped part; and 
 at least one of a metallic filter or a ceramic filter that joins to the hollow-cylindrical member at a base end of the hollow-cylindrical member and on a rear end side with respect to the crimped part, and that at least covers the ventilation hole, wherein said metallic filter or ceramic filter is coated with a water repellent material. 
 
     
     
       2. The gas sensor as claimed in  claim 1 , wherein the at least one of the metallic filter or the ceramic filter is sheet-shaped. 
     
     
       3. The gas sensor as claimed in  claim 1 , wherein the ceramic filter is disposed in the seal member, and wherein a glaze layer is formed on at least a side surface of the ceramic filter. 
     
     
       4. The gas sensor as claimed in  claim 1 , wherein the metallic filter is made of metallic materials selected from the group consisting of stainless steel, copper, copper alloy, nickel, low alloy steel, and aluminum. 
     
     
       5. The gas sensor as claimed in  claim 4 , wherein the metallic filter is made of stainless steel. 
     
     
       6. The gas sensor as claimed in  claim 1 , wherein the water repellent material is a fluorine-based resin. 
     
     
       7. A gas sensor comprising:
 a detection element, extending in the axial direction, that detects a particular gas component in a gas under measurement; 
 a casing surrounding a periphery of the detection element and having a front end from which a front end of the detection element protrudes so that the front end of the detection element is exposed to the gas under measurement; 
 a seal member disposed on a rear side with respect to the detection element and also inside a rear end of the casing, the seal member having a ventilation hole, from one outside surface toward another outside surface; 
 a crimped part of the casing holding the seal member; and 
 at least one of a metallic filter or a ceramic filter being in contact with an inner peripheral surface of the ventilation hole opposite the crimped part and being held by the crimped part, said filter at least covers the ventilation hole and is coated with a water repellent material, 
 wherein a deformation amount of the at least one of the metallic filter or the ceramic filter is from 1% to 50% of a deformation amount of the crimped part. 
 
     
     
       8. The gas sensor as claimed in  claim 7 , wherein the ventilation hole extends in the axial direction from a front end surface of the seal member toward a rear end surface, and wherein the metallic filter or the ceramic filter comprises a covering part covering the ventilation hole and a hollow-cylindrical part connected to the covering part, the hollow-cylindrical part being in contact with the inner peripheral surface of the ventilation hole. 
     
     
       9. The gas sensor as claimed in  claim 7 , wherein the ventilation hole extends in the axial direction from a front end surface of the seal member toward a rear end surface, and wherein the at least one of the metallic filter or the ceramic filter comprises a rod shape that fills the ventilation hole and blocks the ventilation hole. 
     
     
       10. The gas sensor as claimed in  claim 7 , wherein the ventilation hole comprises:
 an axial-direction communicating hole that extends rearward from a front end surface of the seal member in the axial direction; and 
 a radial-direction communicating hole that extends from an outer peripheral surface of the seal member to the axial-direction communicating hole, allowing communication from the front end surface of the seal member to the outer peripheral surface of the seal member, 
 wherein the at least one of the metallic filter or the ceramic filter blocks the radial-direction communicating hole and is in contact with the inner peripheral surface of the axial-direction communicating hole. 
 
     
     
       11. The gas sensor as claimed in  claim 7 , wherein the ceramic filter is disposed in the seal member, and wherein a glaze layer is formed on at least a side surface of the ceramic filter. 
     
     
       12. The gas sensor as claimed in  claim 7 , wherein the metallic filter is made of metallic materials selected from the group consisting of stainless steel, copper, copper alloy, nickel, low alloy steel, and aluminum. 
     
     
       13. The gas sensor as claimed in  claim 12 , wherein the metallic filter is made of stainless steel. 
     
     
       14. The gas sensor as claimed in  claim 7 , wherein the water repellent material is a fluorine-based resin.